Engine

ABSTRACT

A rotary fluid engine powered by externally pressurized working fluid including a rotor and a plurality of swinging arms positioned to engage with and impart a torque force to the rotor when the arms are driven sequentially inward by the selective admission of charges of externally pressurized working fluid. A first segment on the rotor surface engages the free end of each arm as the arm is driven inwardly and a second segment on the rotor surface operates to return the arm outwardly after the power impulse is completed. Valving and conduit means are provided to control the direction of the working fluid to the arms and exhaust means are provided to exhaust spent working fluid from the engine. In one embodiment, the valving and conduit means are adapted to direct charges of externally pressurized working fluid sequentially against said arms so that the engine operates as a simple engine. In a second embodiment, the valving and conduit means are adapted to direct charges of externally pressurized working fluid first against one of said arms at a high pressure and secondly against another arm at a relatively lower pressure so that said engine operates as a compound engine. In a third embodiment, transfer valve means are provided which permit said engine to be switchable between said simple and compound modes of operation. The rotor surface may include a plurality of said first and second segments so that each arm will transmit a corresponding plurality of power impulses to the rotor for each complete rotor revolution.

United States Patent [1 1 Hinckley ENGINE [75] Inventor: John N.Hinckley, Beloit, Wis.

[73] Assignee: Beloit College, Beliot, Wis. 22 Filed: July 24, 1972 21Appl. No.: 274,740

Related US. Application Data [60] Division of Ser. No. 860,684, Sept.24, 1969, Pat. No. 3,684,413, which is a continuation-in-part of Ser.No. 812,656, April 2, 1969, abandoned.

Primary ExaminerCarlton R. Croyle Assistant Examiner-John J. VrablikAttorney, Agent, or Firml-lume, Clement, Brinks, William, Olds & Cook,Ltd.

[57] ABSTRACT A rotary fluid engine powered by externally pressur- [451Apr. 2, 1974 ized working fluid including a rotor and a plurality ofswinging arms positioned to engage with and impart a torque force to therotor when the arms are driven sequentially inward by the selectiveadmission of charges of externally pressurized working fluid. A firstsegment on the rotor surface engages the free end of each arm as the armis driven inwardly and a second segment on the rotor surface operates toreturn the arm outwardly after the power impulse is completed. Valvingand conduit means are provided to control the direction of the workingfluid to the arms and exhaust means are provided to exhaust spentworking fluid from the engine. In one embodiment, the valving andconduit means are adapted to direct charges of externally pressurizedworking fluid sequentially against said arms so that the engine operatesas a simple engine. In a second embodiment, the valving and conduitmeans are adapted to direct charges of externally pressurized workingfluid first against one of said arms at a high pressure and secondlyagainst another arm at a relatively lower pressure so that said engineoperates as a compound engine. ln a third embodiment, transfer valvemeans are provided which permit said engine to be switchable betweensaid simple and compound modes of operation. The rotor surface mayinclude a plurality of said first and second segments so that each armwill transmit a corresponding plurality of power impulses to the rotorfor each complete rotor revolution.

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sum 11 or 12 ENGINE This application is a division of my applicationSer. No. 860,684, filed Sept. 24, 1969, now U.S. Pat. No. 3,684,413,which in turn is a continuation-in-part of my application Ser. No.812,656, filed Apr. 2, 1969, entitled ENGINE, now abandoned, andassigned to the same assignee as the present invention.

The present invention relates to an improved prime mover and moreparticularly relates to an improved rotary engine which is powered byexternally pressurized working fluid and is capable of replacing orsupplementing conventional reciprocating piston internal combustionengines.

As well-known to those skilled in the art, the internal combustionengine in current use has many inherent disadvantages which have causedconsiderable concern about the continued use of that type of an engineas the dominent prime mover. For instance, two principal disadvantagesof internal combustion reciprocating piston engines are low thermalefficiency and poor pollutant emission characteristics. Thesedisadvantages result mainly from the inability of the engine to utilizethe fuel effectively or to complete the combustion of the fuel withinthe expansion chamber of the engine before exhausting the spent fuel tothe atmosphere. Another disadvantage of reciprocating piston engines incurrentv use is inherently low overall mechanical efficiency. It iswell-known, for instance, that the overall efficiency of piston enginesis suppressed to approximately 25 percent by such factors as theinability of the pistons to produce power for about the first 30 andlast 40 of each stroke, and the need for power-absorbing static anddynamic counterbalancing, and parasitic auxiliary systems.

Many attempts have been made to improve upon the thermal characteristicsof reciprocating piston engines. These attempts have included suchefforts as 'major engine redesign to increase the fuel combustion duringexpansion, and suppression of exhaust emissions with parasiticequipment, such as regenerators and the like.

Despite the success of some of these efforts, most reciprocating enginedesigns continue to require expensive fuels and continue to haveunacceptably high pol? -lution characteristics. Efforts to improve thecharacteristics of reciprocating engines have also led to complicateddesigns which are expensive to manufacture, operate and maintain, andwhich continue to have an unsatisfactorily low mechanical efficiency.

The present invention overcomes the abovementioned problems ofreciprocating piston engines by providing a rotary engine which ispowered by externally pressurized working fluid and is capable ofoperating with substantially improved mechanical and thermalefficiencies and substantially improved antipollution characteristics.The rotary engine of the present invention also has a highhorsepower-to-weight ratio and can produce high torque with a smooth andcontinuous flow of power to the output shaft. The structural andfunctional characteristics of this improved rotary engine also permitgreat flexibility of operation thereby allowing the engine to be adaptedfor a variety of applications.

The rotary engine is adapted for use in a power system having acontinuous source of working fluid and means for pressurizing theworking fluid outside of the engine. The system also includes means forfeeding charges of such externally pressurized working fluid into theengine so that the pressurized fluid expands in the engine and creates atorque force which drives the engine output shaft. The externallypressurized working fluid may comprise a compressed gas such ascompressed carbon dioxide, in which case the power system is providedwith means for maintaining the gas under pressure. Alternatively, theextemally pressurized working fluid may be a pressurized vapor such assuperheated steam, and the power system provided with an external heatsource, such as a boiler, for creating the pressurized vapor. Similarly,the power system including the engine may use an open fluid cyclewherein the working fluid is exhausted to the atmosphere after expansionin the engine, or may use a closed fluid cycle which recirculates theworking fluid through the system.

Exemplary Embodiments Additional objects and features of the presentinvention will become apparent from the following'description of severalexemplary embodiments. In the illustrated embodiments, the engine isadapted as a Rankine cycle engine having a closed fluid system whereinenergy is added to the pressurized working fluid by the application ofexternal heat. Superheated steam is the preferred working fluid for theillustrated system, but it will be appreciated by those skilled in theart that alternative working fluids such as mercury 'or organiccompounds reduced to vapor can be utilized with equal effectiveness insuch a vapor cycle system. In some of the illustrated embodiments, theengine rotor is provided with a single lobe, and the engine is adaptedso that each arm transmits one power impulse to the rotor for each rotorrevolution. In other illustrated embodiments, the engine rotor isprovided with double opposed lobes, and the engine is adapted so thateach arm transmits two power impulses to the rotor for each rotorrevolution.

The standard components of the Rankine cycle system, such as the fluidreservoir, the vapor generator for creating the externally'pressurizedworking fluid, the condenser, valves, pumps and heaters, have beenexcluded from the disclosure for purposes of simplicity. The operationof such components to create the pressurized working fluid, such as byconverting water vapor to superheated steam by the application of exter-'the engine are well-known and therefore need not be described indetail.

In the drawings:

FIG. 1 is a partial cross-sectional view of a simple external combustionengine in accordance with this invention embodying a single-lobe rotor,as viewed along the line 11 in FIG. 2;

FIG. 2 is a partial cross-sectional view of the simple externalcombustion engine illustrated in FIG. 1, as viewed from a plane parallelto the output shaft;

FIG. 3 is a partial cross-sectional view of a compound externalcombustion engine in accordance with this invention embodying asingle-lobe rotor, as viewed along the line 3-3 in FIG. 4;

FIG. 4 is a partial cross-sectional view of the compound externalcombustion engine illustrated in FIG. 3 as viewed from a plane parallelto the output shaft;

FIG. 5 is a schematic end view of a valve housing .for the compoundengine which is adaptedto transfer the pressurized working fluid fromone engine expansion chamber to another expansion chamber;

FIG. 6 is a schematic view illustrating the flow of working fluidthrough the compound engine;

FIG.'7 is a schematic end view of a valve housing adapted for use withthe compound engine illustrated in FIGS. 3 and 4 which modifies theengine to permit selective switching between the simple and compoundmodes of operation;

FIG. 8 is a schematic view illustrating the switchable engine operatingas a simple external combustion en-' gine, and further illustrating thevalving and manifold system which permits the engine to be switchedbetween a compound and simple mode of operation;

FIG. 9 is a partial cross-sectional end view of an engine assemblyformed from dual engine units which incorporate a double-lobe rotor andwhich are crosscoupled and offset to form a balanced compound externalcombustion engine;

FIG. 10 is a cross-sectional side view of the compound externalcombustion engine assembly illustrated in FIG. 9, as viewed along theline l in FIG. 9;

FIG. 1 1 is a cross-sectional end view of the engine assemblyillustrated in FIGS. 9 and 10 schematically 7 showing the valving andmanifold systems which adapt the engine assembly for a compound mode ofoperation;

FIG. 12 is a cross-sectional end view of the engine illustrated in FIGS.9 and 10 schematically showingthe valving and manifold systems whichadapt the engine for a simple mode of operation;

FIG. 13 is a partial cross-sectional end view of another embodiment ofthe engine in accordance with this invention incorporating a double-loberotor and six swinging arms which cooperate to form a balanced simpleexternal combustion engine unit;

.FIG. "l4.is a cross-sectional side view of the simple engineillustrated in FIG. 13, as viewed along'the line 14-14 in FIG. 13; 4

FIGS. ISA-D are removed partial sectional views of a suitable adjustablevalve means for selectively controlling the admission and cutoff of theworking fluid in the engine illustrated in FIGSL 13 and 14;

FIG. 16 is a partial cross-sectional end view of still anotherembodiment of the engine incorporating a double-lobe rotor and sixswinging abutment arms which is adapted to be switchable between simpleand compound modes of operation;

FIGQ17 is a cross-sectional side view of the switchable engine as viewedalong the line 17-17 in FIG. 16;

FIG. 18 is a removed end view of the fluid transfer plate incorporatedin the switchable engine illustrated in FIGS. 16 and 17;

FIG. 19 is an end view of the transfer plate shown in FIG. '18schematically illustrating the relationship between the transfer plateand the cut-off valves of the engine assembly.

Single-Lobe Rotor FIGS. 1 and 2 illustrate an external combustion engineembodiment of the present invention having a single-lobe rotor which isadapted for a simple mode of operation, that is there is no compoundingof expansion of the pressurized working fluid before the fluid isexhausted from the engine. This simple engine is designed to utilizesingle charges of pressurized working fluid expanded in the engine forprolonged periods of time, such as throughout about 75 or 80 percent ofthe expansion period. As a result of this mode of operation, the enginehas a high-torque output and is suitable for low-speed high-torqueapplications.

Referring to FIGS. 1 and 2 in more detail, the simple externalcombustion engine is generally indicated by the reference numeral 10.The engine 10 includes a rotor housing 20 containing three pivotedswinging abutment arms A, 40B and 40C and a single-lobe power rotor 50.The arms 40A-C are pivotally mounted on pins 4lA-C (FIG. I) and therotor is pivotally mounted on a central drive shaft 30. Such pivotalconnections for the arms 40A-C and rotor 50 are accomplished by keys orsplines and are free-floating connections which permit the arms androtor to float laterally and maintain a position of equilibrium withinthe housing 20 during the operation of the engine.

As indicated in'FIG. l, the rotor housing 20 and the interior surfacesof the arms 40A-C cooperate to define a generally cylindrical chamberwithin which the rotor SO'can rotate. Generally, during the operation ofthe engine a pressurized working fluid such as high pressure superheatedsteam is directed into the interior of the rotor housing 20 in a mannerwhich forces the arms 40A-C sequentially inwardly against the surface ofthe rotor 50. The expanding working fluid works against the arms 40A-Cand the exposedsurface of the rotor 50 to thereby impart a rotationaldriving force to the rotor, and the rotor in turn transmits an outputtorque to the drive shaft 30.

As seen in FIG. 2, one end of the rotor housing 20 is closed by aflywheel housing 60 and the other end is I closed by a valve housing'70. The housings 60 and 70 include centrally positioned main bearings6l and 71, respectively, which support the drive shaft 30. The housings60 and 70 also inciude machined end plates 62and 72, respectively, whichseal the adjacent ends of the rotor housing 20. Suitable head bolts andgasketing (not shown) are provided to assure thatthe plates 62 and 72seal the rotor housing 20 effectively. The

, plates 62 and 72 also pivotally support the pivotpins 4lA-C (FIG. 1)about which the arms 40A-C pivot for operating the engine accessories. Alubricator pump 66, driven by the pinion 65, is connected to asequentially-metered lubrication system (not shown) which meters thenecessary amount of lubricating oil to each surface such as the bearings61 and 71 requiring lubrication. Inspection plates 67 and 68 are alsoprovided on the flywheel housing 60 to permit access to the interior ofthe housing for inspection and repair.

As shown in FIG. 2, the rotor 50 and arms 40A-C of the engine inaccordance with this invention are closely machined to haveapproximately the same width as the rotor housing 20. This designprovides for a large surface area on the rotor 50 and arms 40A-C forcontact with the working fluid during the operation of the engine.Moreover, by this arrangement the rotor and arms are positioned in thehousing and spaced from the plates 62 and 72 only by a close tolerance.Sealing means thus can be provided between the sides of the arms 40A-Cand rotor 50 and the plates 72 and 62 to prevent leakage of any workingfluid past the rotor or arms.

In the preferred embodiment of the invention, labyrinth sealing is usedto seal the sides of the rotor 50 and arms 40A-C with respect to theendplates 62 and 72. Such labyrinth sealing eliminates the need forlubricating moving parts such as piston rings or seals and isaccomplished by providing a series of short labyrinth grooves 52 on thesides of the rotor 50 and similar grooves 42 on the sides of each of thearms 40A-C. The grooves 42 and 52 are arranged to follow the profile ofthe associated arms or rotor so that each groove acts as a check valveto stop the flow of working fluid past the arms or rotor in theclearance adjacent the plates 62 and 72. The short labyrinth grooves 42and 52 also prevent the working fluid from traveling along the fulllength of the rotor or arms. The above-described-freefloatingconnections for the arms 40A-C and rotor 50 assist the scaling functionof the labyrinth grooves 42 and 52 by allowing the arms and rotor to beselfcentering within the housing 20. The effectiveness of the labyrinthgrooves 42 and 52 is further assisted by designing the rotor 50, arms40A-C and housing 20 so as to have substantially equal coefficients ofexpansion. The clearance between the plates 62 and 72 and the rotor andarms therefore will be substantially constant of which is associatedwith each of the arms 40A-C.

Each admission chest 74A -'C is connected to a vapor generator (notshown) or another suitable source of high pressure fluid by means ofintake pipes 75. As

shown in FIG. 2, the chests 74A-C also are in fluid communication withan expandable chamber defined by the rotor housing 20 and the associatedarm 40A-C through intake manifolds 76 provided in the valve housing 70and through aligned intake chambers 22 provided in the rotor housing 20.The intake chambers 22 are spaced within the housing 20 (FIG. 1) so thatthe pressurized working fluid enters the rotor chamber at a locationclosely adjacent the free end of the associated arms 40A-C. By thisarrangement, the entering charge of fluid initially contacts theassociated arm at a point of great leverage and is capable of forcefullyswinging the arm inwardly against the rotor 50. As seen in FIG. 1, thefree end of the arms 40A-C seal the associated intake chamber 22 closedwhen the arm is in th outermost position.

The valve housing 70 also contains a valve mechanism for controlling thetiming and rate at which the pressurized working fluid is admitted intothe chests 74A-C. To accomplish such timing and metering, each of .thechests 74A-C is separated from the associated intake manifold 76 by apoppet valve 77. The stroke of regardless of the engine load oroperating temperature.

As illustrated in FIG. 1, the free end of each of the arms A-Cincludes'a bevelled portion 43 which allows the associated arm to engagewith the rotor 50 along a flat and highly machined contact surface. Thissubstantial contact surface on the arms 40A-C is held against the rotor50 by the force of the expanding working fluid and is sufficient toprevent any substantial leakage between the arms and rotor. The bevelledportion 43 also allows the rotor and arms to withstand a high loadingforce by distributing the force of the expanding working fluid over alarge area of contact on the arms and rotor.

Each arm 40A-C has a projection 46 on its inner surface which definesthe point closest to the associated pivot pin 41AC at which the rotorwill engage with the arm. Such an arrangement assures that the forces ofthe rotor 50 will act on the arms 40A-C at a point of substantialleverage. A relief 47 is provided on each arm 40A-C to allow clearancefor the rise 57 of the rotor to pass by the arms. Sealing strips 44 areprovided to seal the arms 40A-C with respect to the rotor housing 20adjacent the pivoted end of the arms, as shown in FIG. 1. The strips 44thereby separate the expansion and exhaust phases of the working fluidduring the operation of the engine.'

The engine 10 in accordance with this invention also is provided with avalving mechanism which admits the charges of pressurized working fluidinto the rotor housing 20 in the proper sequence. In the illustratedembodiment, for instance, the pressurized working fluid is admitted in apattern which swings the arms 40A, 40B and 40C inward sequentiallyagainst the rotor 50, and drives the rotor clockwise in FIG. 1. Toachieve such control of the working fluid, the valve housing 70 containsfluid admission chests 74A-C, one

each poppet valve 77 is controlled by cams 78 provided on the driveshaft 30. A conventional gearing mechanism 79, such as the Stephensonmechanism illustrated schematically in FIG. 2, connects the valves 77 tothe.

cams 78 and permits the closing stroke of the valves 77 to be adjustedto vary the rate or quantity of working fluid supplied to the engine. Aswell-known to those skilled in the art, such a variable cutoff mechanismcan be operated either manually or automatically to vary the operatingchracteristics or the performance of the engine 10. A cover plate 80closes the valve housing 70 and protects the above described valvemechanism from damage.

The engine 10 also includes an exhaust system for discharging the spentworking fluid from the expandable chamber defined by the rotor housing20 and each arm 40A-C. In this regard, the valve housing 70 is providedwith a plurality of exhaust manifolds 92 which are spaced uniformlyabout the housing to receive the spent working fluid from the threesegments of the'engine 10. In addition, the end plates 62 and 72 of thehousings 60 and 70 are provided with uniformly spaced exhaust ports A-C.As indicated in FIG. I, an exhaust port 90 is positioned near thepivoted end of each of the adjacent arms 40A-C. Each port 90 is in fluidcommunication with the adjacent exhaust manifold 92 and can therebyoperate to discharge the working fluid from the expandable chamberassociated with the preceding arm. The fluid is thereby exhausted into asuitable condenser or the like, from which the fluid is fed to a vaporgenerator and re-pressurized forrecirculation through the engine.

The ports 90A-C are designed to be sufficiently large to permit rapidexhaustion of the spent working fluid with a minimum loss of energy.Further, the ports 90A-C are positioned to permit the power impulses onthe rotor 50 to overlap, so that the operation of the engine 10 issmooth andthe application of torque to the rotor 50 is continuous.

To eliminate the need for auxiliary exhaust valve mechanisms, the engine10 includes valving portions 40AC, to control the opening and closing ofthe associated exhaust ports 90A-C. As illustrated in FIG. 1, thevalving portions 45A-C extend beyond the arm pivot pins 41A-C to coverthe adjacent exhaust port 90A-C when the associated arm is in itsoutermost position (See arm 403, FIG. 1). The valving portions 4SA-Cswing away to open the ports 90A-C when the associated arm 40AC swingsinto its innermost position (See arm 40C, FIG. 1). The valving portions45A-C are designed so that the opening and closing of the exhaust ports90A-C are coordinated with the positioning of the arms 40A-C and therotor 50 during the operation of the engine 10. I

The rotor housing 20 has recesses 25 to receive the valving portions45A-C as the arms 40A-C move inwardly toward the rotor 50. The sealingstrips 44 frictionally engage with the associated arm and prevent thepressurized working fluid from becoming trapped within the recess 25.The recesses 25 preferably are vented to theatmosphere by suitable means(not shown) so that any working fluid which may enter the recesses isexhausted without inhibiting the action of the associated arm.

1n the preferred embodiment of this invention, the rotor 50 is adaptedto control the sequence of movement of the arms 40AC to overlap thepower impulses transmitted to the rotor so that the flow of power to therotor 50 is smooth and continuous. The rotor 50 also controls the inwardand outward movement of the arms so that the swinging motion of each armclosely approximates a simple harmonic motion. Such arm movementminimizes the amount of energy absorbed by inertia losses resulting fromthe rapid reversal of the arms.

The surface of the-rotor S is designed to engage with the bevelledportions 43 of the arms 40A-C to receive a power impulse from the armsand to control the sequential movement of the arms during the operationof the engine. To accomplish these functions, the rotor 50 includes anose or high point 53 positioned to engage with the adjacent arm 40A-Cand maintain the arm in its outermost position for a selected timeperiod (See arm 408, FIG. 1). Further, the surface of the rotor definesa fall segment 54 which isengaged by the arms 40A+C as the arms aredriven inwardly by the force of the working fluid (See arm 40A, FlG. l).The fall segment 54 has a configuration which causes the arms 40A-C- tomove inwardly with approximately simple harmonic motion. The arm fallsegment 54 terminates with asloping .portion 55 which decelerates theinwardly moving arm and prepares the arm for a reversal of direction. Y

The sloping portion 55 leads the inwardly moving arm 40A-C to a lowdwell segment 56 on the surface of the rotor 50. The low dwell segment56 is concentric to the axis of rotation of the rotor 50 and extendsalong the rotor surface for a selected number of degrees. The dwellsegment 56 thereby stops the inward movement of the arms 40A-C anddefines the limit for inward arm travel.

Since the three arms 40A-C in the illustrated engine are spaced 120apart, the cycle of operation for the arms will be 120 out-of-phase, andthe movement of adjacent arms will be separated by 120 of rotorrotation. Thus, each of the arms 40A-C will complete its inwardmovement, and traverse the fall segment 54 from the high point 53 to thelow dwell segment 56, as

- the rotor 50 rotates through 120. However, in the preferredarrangement the fall segment 54 is designed to complete the inwardmovement of the arms 40A-C as the rotor rotates for less than 120, forinstance This arrangement allows the arms to decelerate smoothly andassures that the stroke of one arm, such as arm 40A, is completed beforethe exhaust cycle is started by movement of the adjacent arm.

The movement of the adjacent arm (arm 403) will start after of rotationof the rotor 50, but the valving portion 45 of the arm and theassociated exhaust port 90 are arranged so that exhaust does not startuntil that arm moves through a small arc, such as l020. This designpermits an overlapping of the power impulses, to obtain optimum torqueon the rotor 50., by preventing the exhaust ports 90 from openingprematurely.

The overlapping of the power impulses on the rotor 50 is assisted bydesigning the low dwell segment 56 of the rotor 50 with an arc of 10 to20 so that the arms 40A-C contact the segment for a short time after therotor has rotated beyond 120. The dwell segment 56 thereby precludesoutwardmovement of the engaged arm 40 until after the power strokes ofthe adjacent arms (e.g., 40A and 4013) have overlapped and theassociated exhaust port 90 has opened. This arrangement of the dwellsegment 56 also allows the working fluid to expand fully against theinwardly moving arm 40 and roto 50 before the arm starts to move outwardand force the fluid into the exhaust system.

The next segment of the rotor 50 which engages with the arms 40AC is arise segment 57 which is designed to force the engaged arm outwardlyfrom its innermost position (See arm 40C, FIG. 1) toward its outermostposition (See arm 408, FIG. 1) with simple harmonic motion. The risesegment 58 preferably is designed to drive the arms 40A-C outwardly asthe rotor 50 rotates through approximately ninety additional degrees.

The remaining surface of the rotor 50 between the rise segment 57 andthe high point 53 comprises a high dwell segment 58. T his segment 58 isconcentric with the axis of the rotation of the rotor 50, and isdesigned to maintain the adjacent arm 40 in its outermost position (Seearm 40B) through approximately of rotation of the rotor 50. The rotor 50then has rotated 360 with respect to the arms 40, and is in aposition'to repeat its operating cycle. The above-described rotorsegments thereby provide the rotor 50 with a single lobe, having a highpoint 53 which allows each arm 40A-C to complete. its cycle of movementonce for eachrevolution of the rotor. By this arrangement, each arm40A-C will transmit one power impulse to the rotor 50 per rotorrevolution.

In operation, the swinging arms 40A-C transmit torque to the rotor 50 inproportion tothe force imposed upon the outward sides of the arms by thepressurized working fluid. The rotor 50 and arms 40A-C further act toseal the fluid expanding in one segment of the engine 10 from the fluidexhausting from another engine segment. This functionalinterrelationship between the arms 40 and the rotor 50 will beunderstood from a description of the operation of the engine through.one complete cycle. Since the engine 10 consists of three symmetricalsegments, each including one of the arms 40A-C, the cycle could startwith any one arm. Fur purposes of illustration, the operation of theengine will bedescribed with reference to a cycle initiated by admittinga charge of steam through the steam chest 74A to act upon the arm 40A.

To begin the engine operation, the valve gear mechanism 79 is adjusted,either manually or automatically, to introduce a charge of steam throughthe chest 74A at the desired rate. The mechanism 79 can be varied to cutoff the steam charge after the rotor 50 rotates through a few degrees orafter the maximum 120 of rotor rotation. As well-known by those skilledin the art, a longer cutoff time introduces a greater quantity ofworking fluid into the rotor chamber and increases the power output ofthe engine.

The valve mechanism 79 and the rotor 50 are timed so that the steamcharge is admitted through the chest 74A and the associated channel 22as the high point 53 of the rotor 50 passes the bevelled portion 43 onthe free end of the arm 40A. The entering steam expands against the arm40A and the rotor 50 and forcefully drives the arm 40A inwardly againstthe rotor. The expanding steam thereby imparts a torque force to therotor 50, and drives the rotor and the shaft 30 (in a clockwisedirection in FIG. 1). as seen in FIG. 1, the engagement of the rotor 50with the arms 40A and 40B seals the resulting expandable steam chamber(the increased volume below arm 40A) from the remaining portion of therotor chamber.

In the illustrated engine 10, the fall segment 54 on the rotor 50 allowsthe arm 40A to move inwardly as the rotor 50 rotates throughapproximately 110. The motion of the arm 40A is then decelerated by therotor sloping portion 55. The inward motion of the arm 40A is finallystopped when the arm engages the low dwell segment 56. In thisembodiment, the arm 40A remains engaged with the segment 56 and remainsin its innermost position until the rotor 50 rotates an additional 20,or through a total are of 130.

Simultaneous with the above-described operations, the valve mechanism 79operates to admit a second charge of superheated steam to the chest 74Band into the expandable chamber defined between the second arm 40B andthe rotor housing 20. When the rotor 50 has traveled through 120 andthereby moved the rotor high point 53 past the bevelled portion 43 onthe arm 408, the second charge of steam forces the arm 408 inwardlyagainst the rotor. By this arrangement, a second power impulse beginsagainst the rotor 50 at 120 of rotor rotation. Furthermore, the valvingportion 458 on the arm 40B and the associated exhaust port 908 aredesigned so that the port 908 is not opened until the rotor 50 has movedbeyond the free end of the arm 408. Thus, the first steam charge in theexpandable chamber associated with the preceding arm 40A continues toexpand and impart a torque to the rotor for this additional 10, andoverlaps with the force of the second steam charge during that interval.

In the illustrated engine 10, the first arm 40A engages the rotor risesegment 57 afte 130 of rotor rotation. Continued rotation of the rotorthrough 90 drives the first arm 40A outwardly and permits the secondarm40B to be forced inwardly. The outwardly moving arm 40A will therebyscavenge the first charge of steam and discharge the steam through theenlarging exhaust port 90B. Further rotation of the rotor 50 through theremaining 140 brings the high dwell segment 58 into engagement with thearm 40A. The arm 40A is thereby maintained in its outermost positionwhile the cycle for the second arm 40B is being completed.

The same cycle of operation as described above for the arm 40A isfollowed by-the arm 40C. It will be readily understood, however, thatthe cycle for the third arm 40C follows the cycle of arm 405 by 120, andleads the cycle for arm 40A by the same amount.

To illustrate the high torque characteristics of the .simple engine 10in accordance with this invention,

various engine operating parameters were fed into a computer which wasprogramed to calculate the expected performance of an engine having arotor chamber with a four inch width and a 7.5 inch internal diameterand having the single-lobe rotor shaped as generally shown in FIGS. 1and 2. In one computer example, th incoming steam pressure was selectedas 200 psi gauge pressure, and the steam cutoff was selected to occur ineach segment of the engine after the rotor had traveled through 110. Thesteam was allowed to expand through 130 of rotor rotation to provide anoverlap in the power impulses from the adjacent engine sections. Thecomputerized data projected that under these conditions the steampressure would drop to 179 psig after the steam is fully expandedthrough 130 and would then be exhausted. The computerized data alsoprojected that the ,mean output torque for the engine was 7,421 inchpounds, with a resultant power output of 141 indicated horsepower at1,200 rpm.

In another computerized example, the same simple engine was analyzedwith 200 psig steam being admitted with the cutoff adjusted to 55 ofrotation of the rotor. In this example, the steam was allowed to expandfor an additional of rotor rotation and was finally exhausted at apressure of 72 psig. The projected characteristics for this engine werea mean output torque of 5,815 inch pounds, with a resultant power outputof 111 indicated horsepower at 1,200 rpm.

Similar computerized data also estabished that the power output of theengine in accordance with this invention is directly proportional to therotor width and speed, and the pressure of the incoming charge ofexternal working fluid. If any of these parameters are doubled, forinstance, the resulting power output of the Compound Engine Single-LobeRotor FIGS. 3 through 6 illustrate an external combustion engine havinga single-lobe rotor which is adapted for a compound mode of operation.In this compound engine each charge of pressurized working fluid isexpanded twice in the engine. Since each expansion of the pressurizedfluid transmits torque to the rotor, the compound engine has excellentfuel economy and can operate at high speeds for a sustained period. Thecompound expansion of each charge of working fluid also minimizes thecondensation of the fluid within the engine when the engine is operatedwith. superheated steam.

Referring to FIGS. 3-6 in more detail, the compound external combustionengine includes many of the same components as the above-describedsimple engine 10. A rotor housing contains three pivoted swingingabutment arms A, 1408 and 140C, and a single-lobe power rotor 150. Thearms l40A-C are pivotally mounted on pins 14lA-C, and the rotor 150 ismounted for rotation on a central drive shaft 130. The connections forthe arms 140AC and rotor 150 comprise keys or splines or the like whichpermit the arms and rotor to float freely in the lateral direction, andbe self-centering within the housing 120. The rotor housing 120 and theinterior surfaces of the arms 140A-C define a generally cylindricalchamber within which the rotor 150 will rotate during the operation ofthe compound engine 100.

As illustrated in FIG. 4, one end of the rotor housing 120 is closed bya flywheel housing 160 and the other end is closed by a valve housing170. The housings I60 and 170 include main bearings 161 and 1711,respectively, and define end plates 162 and 172 which seal the adjacentends of the rotor housing. The end plates 162 and 172 support the pivotpins 141A-C (FIG. 3) about which the arms 140A-C rotate. The housing 160contains a counterweighted flywheel 163 which is keyed to the driveshaft 130. Accessory drive gears and pinions 164 and 165 are alsoprovided in the housing 160 for driving the engine accessories, such asa lubricating pump 166, in the well-known manner. The housing 160 alsoincludes removable inspection plates 167 and 168.

As shown in FIG. 4, the rotor 150 and the arms 140A-C of the engine 100have approximately the same width as the rotor housing 120. Thisarrangement provides a large surface area on the rotor and arms forcontact with the working fluid, and spaces the rotor and arms within avery close tolerance to the end plates 162 and 172.. The rotor and armsthereby can be sealed with respect to the end plates 162 and 172 by aplurality of short labyrinth grooves 142 and 152. As described above,the labyrinth grooves 142 and 152 follow the profile of the associatedarm or rotor, and act as check valves to stop the flow of working fluidpast the rotor and arms. The arms 140A-C, rotor 150 and housing 120 arealso designed to have substantially equal coefficients of expansion, sothat the operation of toward the rotor 150. The sealing strips 144prevent the working fluid from becoming trapped within the recesses 125.The recesses 125 also are vented to the atmosphere by suitable means(not shown).

As illustrated by the position of the arm 1408 in FIG. 3, the valvingportions 145AC are arranged to close the adjacent exhaust portlA-C whenthe associated arm is in its outermost position. The valving portions145A-C swing outwardly to open the adjacent port l90A-C when theassociated arm swings into its innermost position. The operation of theexhaust ports l90A-C is controlled by the positioning of the arms 140A-Cand the rotor 150.

Each of the arms 140A-C inthe compound engine also includes an outwardlyprojecting horn member 148. The horn members 148 are integral with theassociated arm'and are designed to extend outwardly from the arm for adistance which exceeds the length of the inward arm stroke. The horns148 are formed adjacent the free end of the arms, and terminate todefine a substantially flat contact surface 149 on the outer end of eacharm. As clearly illustrated in FIG. 3, each horn 148 has outwardlyconverging side edges which'give the horn an outwardly tapered orwedge-shaped configuration.

The rotor housing is formed with a plurality of horn recesses '128 toaccommodate the projecting horns 148 The recesses 128 also have ataperedshape which closely conforms to the shape of the horns 148 so that eachrecess will receive the adjacent horn when the associated arm A-C isinits outermost position (See arm 1408, FIG. 3). Further, as indicated bythe arm 140C in FIG. 3, the horns 148 and recesses 128 are arcuate inshape so that the horns are in sealing engagement with the rotor housing120 as the associated arm l40A-C moves inwardly toward the rotor 150.The tapered'shape of the horns 148, which provides the horns with anarrow width at their outer ends and a broader the labyrinth scaling isunaffected by engine load or operating temperature.

As illustrated in FIGS. 3 and 6, each of the arms l40A-'C- includes abevelled portion 143 at its free end for contacting the surface of therotor 150. Each arm also includes a projection 146 on its inner surfacewhich prevents the rotor 150 from engaging with the arms at any pointcloser to the associated pivot pin l4lA-C. The rotor 150 will therebyengage each arm l40A-C at the high leverage section between the bevelledportion 143 and the projection 146. Each arm l40A-C also includes arelief 147 which provides clearance for the rise 157 of the rotor topass by the arms. Further, sealing strips 144 are provided in the rotorhousing 120 to engage with the adjacent arm 140A-C and seal theexpansion chambers of the engine from each other and from the exhaustchambers.

The lower end of each arm 140AC also defines exhaust valving portions 145AC which move with the arms 140A-C and control the opening and closingof an associated exhaust port 190A-C. The exhaust ports 190A-C are castin the face plates 162 and 172 of the gear housing and the valve housingand are connected to a fluid condenser or the like through exhaustmanifolds 192. Recesses 125 receive the valving portions 145A-C as theassociated arm moves inwardly width at their inner ends, preventsthe'development of a partial vacuum in the horn recesses 128 whichotherwise would inhibit the inward movement of the arms.

Since the extent of the horns 148 exceeds the length of the stroke ofthe arms l40A-C,the horns will remain in sealing engagement with therotor housing 120 throughout the operation of the engine. By thisarrangement, the space in the recess 128 behind-each arm 140A-C and theadjacent intake chamber 122 define a closed chamber which expands involume as the associated arm l40A-C moves inwardly toward the rotor 150.In accordance with this invention, such chambers behind the arms l40A-Cdefine high pressure chambers HP I-IP and HP respectively, which willreceive a charge of working fluid at high pressure during operation ofthe compound engine 100.

In accordance with this invention, the engine 100 also is provided withlow pressure chambers for receiving a charge of working fluid such assteam from each of the high pressure chambers I-IP,, to thereby compoundthe effect of the charge on the rotor 150. In the illustrated engine100, the volume of the low pressure chambers LP is approximately one andone half to two and one half times the volume of the associated highpressure chambers HP However, this ratio may be varied over a broadrange by varying the desing of the arms 140AC and the rotor 150.

To provide the low pressure chambers, the rotor housing 120 is cast toinclude uniformly spaced fluid channels 129. As shown in FIGS. 3 and 6,each channel 129 is positioned so that one end is in communication withthe contact surface 149 on the adjacent arm 140AC, and the other end isin communication with an intake chamber 173 cast in the valve housing170. By this arrangement, the working fluid expanding in the channel 129will press against the adjacent surface 149 and urge the adjacent arminwardly against the rotor 150. Further, as indicated by the arrangementof the arm 140A in FIGS. 3 and 6, the rotor and adjacent arms define anexpanding, sealed chamber which is in communication with the adjacentchannel 129. Thus, each segment of the compound engine 100 is providedwith an expanding low pressure chamber, designated respectively aschambers LP ,-LP and LP which is sealed from the main portion of therotor chamber by the adjacent arm l40A-C and the rotor 150, and sealedfrom the adjacent high pressure chamber HP by the adjacent arm horn 148.In addition, as seen in FIG. 3, each of the low pressure chambers LI,,is position adjacent one of the exhaust ports l90A-C. The charge ofworking fluid therefore can be exhausted through the adjacent port 190after the expansion of the fluid in the low pressure chamber iscompleted.

The engine 100 also includes a manifold and valving system forcontrolling the admission of the pressurized working fluid into the highpressure chambers HP and for transferring the fluid, after expansion inthe high pressure chambers, to the low pressure chambers Islwhere thefluid is expanded further before being exhausted from the engine. Inthis regard, the valve housing 170 includes a plurality of admissionchests 174A-C which are arranged uniformly around the rotor 150. Asshown in FIGS. 3 and 6, each chest 174A-C is in fluid communication withone of the high pressure chambers I-IP through a high pressure manifold176 which is aligned with the intake chamber 122. Intake pipes 175connect each manifold 176 with a vapor generator (not shown) or othersuitable source of high pressure fluid.

Timing and metering of the incoming pressurized fluid is accomplished byseparating the chests l74A-C from the associated intake manifold 176 bya poppet valve 177. The stroke from each valve 177 is controlled by cams178 connected to the drive shaft 130 and by a Stephenson-type variablegearing mechanism 179. A cover plate 180 encloses the valve housing 170to protect the above-described valving and manifold system from damage.

As illustrated in FIGS. 5 and 6, the valve housing 170 also includestransfer channels 194A, 1948 and 194C for transferring the working fluidfrom the high pressure chamber HP of one of the arms l4 0A-C to the lowpressure chamber LP of the adjacent arm. More specifically, the transferchannel 194A extends across the housing 170 and connects the highpressure chamber I-IP directly to the low pressure chamber LP In a likemanner, the channel 194B connects thehigh pressure chamber I-IP with thelow pressure chamber LP and the channel 194C connects the high pressurechamber HP with the low pressure chamber LP,,. In the preferredembodiment of this invention, no valving is needed between the highpressure chambers HP and the associated transfer channel l94A-C. Theinitial charge of working fluid entering the high pressure chambers willfill the transfer channels. Then, the motion of the rotor 150 and armsl40A-C will control the transfer of the fluid charge through thechannels from the high to the low pressure chambers, and the exhaust ofthe fluid from the low pressure chambers.

In the preferred embodiment wherein the compound engine is operated withsteam or the like, the pressure chambers HP,, and LP the transferchannels l94A-C the rotor 150 and the arms A-C are designed so that thechange in volume of the low pressure chambers LP is at the same rate asthe change in vol- I ume of the associated high pressure chamber HP. Asa result, substantially no work will be done on the fluid during thetransfer and there will be substantially no energy loss during thetransfer phase of the engine operation. In the alternative, if thethermodynamic characteristics of the working fluid require it, the fluidcharge could be circulated through a suitable reheating system (notshown) or the like before the transfer through the channels l94A-C iscompleted.

The surface of the rotor controls the movement of the arms 140A-C sothat each arm swings with approximately simple harmonic motion, and theinertia losses resulting from the rapid reversal of the arms isminimized. In the preferred embodiment, the rotor 150 also controls thesequence for the arms l40A-C so that the power impulses transmitted tothe rotor are overlapping.

Accordingly, the rotor 150 includes a high point 153 which will engagewith the adjacent arm l40A-C and maintain that arm in its outermostposition for a selected period (See arm 140B, FIG/3). An arm fallsegment 154 on the rotor 150 engages the arms l40A-C as the arms aredriven inwardly by the force of the working fluid (See arm 140A, FIG.3). The fall segment 154 is shaped to move the arms inwardly withapproximately simple harmonic motion, and terminates with a slopingportion 155 which decelerates the inwardly moving arm at the end of thepower stroke. The sloping portion 155 leads the inwardly moving arml40A-C to a low dwell segment 156 on the rotor 150. The low dwellsegment 156, which defines the inner limit for the arms 140AC, isconcentric to the axis of rotation of the rotor 150 and extends alongthe rotor for a selected number of degrees.

In the illustrated compound engine 100, where the arms DNA-C areuniformly spaced by I20", the movement of adjacent arms will be 120out-of-phase. Accordingly, each arm will complete its inward movementand traverse the fall segment 154 from the high point 153 to the lowdwell segment 156, as the rotor 150 rotates through 120 degrees. In thepreferred arrangement, the fall segment 154 is shaped to complete theinward stroke of each of the arms as the rotor rotates through an areslightly less than 120, such as l l0. Such an arrangement deceleratesthe arm smoothly and allows the arm to rest against the low dwellsegment 156 before the direction of movement of the arm is reversed.

The next segment of the rotor 150 to engage with the arms l40A-C is anarm rise segment 157. The rise segment 157 sequentially engages each ofthe arms l40A-C and forces the arm outwardly from its innermost position(See arm 140C, FIG. 3), toward its outermost position (See arm 1408,FIG. 3) with approximately simple harmonic movement. In the illustratedengine 100, the rise segment 157 is designed to com-

1. A rotary externally pressurized fluid engine comprising: a housingdefining a generally cylindrical rotor space having parallel end walls;a rotor mounted on a shaft within said rotor space, said rotor having asubstantial transverse surface and side portions spaced adjacent saidend walls; a plurality of elongate arms positioned within conforming armrecesses provided around the inner periphery of said housing and spaceduniformly with respect to said rotor, each of said arms having sideportions spaced adjacent said end walls and further having one endpivoted to said housing and the other end free to swing between anoutward position engaged within the associated arm recess and an inwardposition engaged with said rotor surface; a horn member provided on eachof said arms intermediate said arm ends and projecting outwardly intothe associated arm recess, each of said horn members being positioned toslide in the associated recess in sealing engagement with said housingas said arms move between said inward and outward positions; said rotorsurface including a first segment sequentially engageable with the freeends of said arms as said rotor rotates to permit said arms to moveinwardly from said outward position and a second segment sequentiallyengageable with the free ends of said arms as said rotor continues torotate to return each arm to said outward position; a plurality of firstexpandable fluid chambers defined between said housing and said rotoradjacent the free ends of said arms; a plurality of second expandablefluid chambers defined by said arm recesses and the associated arms andsealed from said first chambers by said arm horn members; transferchannels connecting each second fluid chamber in flUid communicationwith a first fluid chamber associated with another arm; conduitsconnecting each first fluid chamber in fluid communication with thesecond chamber associated with the same arm; transfer valve means influid communication with said first chambers and selectively operable inone position to sequentially direct charges of said pressurized fluidinto said chambers so that said charges operate simultaneously in thefirst and second chambers connected to said conduit means when saidfirst segment of said rotor is positioned adjacent the free end of theassociated arm, to operate said engine as a simple engine, said transfervalve means being further operable in a second position to sequentiallydirect charges of said pressurized working fluid into said secondchambers for initial operation in said second chambers when said firstsegment of said rotor is positioned adjacent the free end of theassociated arm so that the following movement of said arms changes thevolumes of the first and second charges from said second chambers tosaid first chambers through said transfer channels, to permit saidcharges to operate further in said first chambers and thereby operatesaid engine as a compound engine; exhaust means in fluid communicationwith each first fluid chamber and arranged so that outward movement ofsaid arms forces the fluid from said second chambers into the connectedfirst chamber and forces the fluid from said first chambers through saidexhaust means; and means sealing said side portions of said rotor andarms with respect to said housing end walls; whereby said transfer valvemeans permits said engine to be switchable between simple and compoundmodes of operation.
 2. A rotary externally pressurized fluid enginecomprising: a housing defining a pair of generally cylindrical rotorchambers having end walls; a pair of double-lobe rotors mounted on acommon shaft so that one of said rotors is positioned in each of saidrotor chambers, said rotors having substantial transverse surfaces andside portions spaced adjacent said end walls; four elongate armsuniformly spaced around the inner periphery of said housing in each ofsaid rotor chambers within conforming arm recesses provided in saidhousing; each of said arms having side portions adjacent said end wallsand further having one end pivoted to said housing and the other endfree to swing between an outward position engaged within the adjacentarm recess and an inward position engaged with the adjacent rotorsurface; a tapered horn member provided on each of said arms adjacentsaid free arm ends and projecting outwardly into the adjacent armrecess, each of said horn members having outwardly converging edges withone edge being positioned to slide in sealing engagement with saidhousing as said arms move between said inward and outward positions;said surface of each of said rotors including a pair of diametricallyopposed first segments sequentially engageable with the free ends of anopposed pair of the associated arms to permit said engaged pair of armsto move inward and transmit a torque force to said rotor, each rotorfurther including a pair of diametrically opposed second segmentssequentially engageable with the free ends of said opposed pair of armsto return said pair of arms to said outward position; a plurality offirst expandable fluid chambers defined by said housing adjacent thefree ends of each of said arms; a plurality of second expandable fluidchambers defined by said arm recesses and the associated arms and sealedfrom said first chambers by said arm horn members; transfer channelsconnecting each second chamber in one of said rotor chambers in fluidcommunication with the axially adjacent first chamber in the other rotorchamber; conduits connecting each first chamber in fluid communicationwith the second chamber associated with the same arm in the same rotorchamber; transfer valve means in fluid Communication with said firstchambers and selectively operable in one position to sequentially directcharges of said pressurized fluid into said chambers so that saidcharges operate simultaneously against a pair of opposed arms in thefirst and second chambers connected by said conduits when said firstrotor segments are positioned adjacent the free ends of the pair ofarms, to operate said engine as a simple engine; said transfer valvemeans being further operable in a second position to sequentially directcharges of said pressurized working fluid into said second chambers forinitial operation in said second chambers against a pair of opposed armswhen said first rotor segments are positioned adjacent the free ends ofthe pair of arms so that the following movement of said pair of armschanges the volumes of the first and second chambers connected by saidtransfer channels and transfers said initial charges from said secondchambers to said connected first chambers through said transferchannels, to permit said charges to operate further in said firstchambers and thereby operate said engine as a compound engine; exhaustmeans in fluid communication with each first fluid chamber and arrangedso that outward movement of said arms and continued rotation of saidrotors forces the fluid from said second chambers into the connectedfirst chambers and forces the fluid from said first chambers throughsaid exhaust means; and means sealing said side portions of said rotorsand arms with respect to said housing end walls; whereby the operationof said charges in one of said rotor chambers will overlap the operationof said charges in the other rotor chamber, and whereby said engine isswitchable between simple and compound modes of operation.
 3. A rotaryexternally pressurized fluid engine comprising: a housing defining agenerally cylindrical rotor space having parallel end walls; a rotormounted on a shaft within said rotor space, said rotor having asubstantial transverse surface and side portions spaced adjacent saidend walls; a plurality of elongate arms positioned within generallyconforming arm recesses provided around the inner periphery of saidhousing and spaced uniformly with respect to said rotor, each of saidarms having side portions spaced adjacent said end walls and furtherhaving one end pivoted to said housing and the other end free to swingbetween an outward position engaged within the associated arm recess andan inward position engaged with said rotor surface; a tapered hornmember provided on each of said arms adjacent said free arm ends andprojecting outwardly into the associated arm recess, each of said hornmembers having outwardly converging side edges, with one edge beingpositioned to slide in sealing engagement with said housing as said armsmove between said inward and outward positions; said rotor surfaceincluding a first segment sequentially engageable with the free ends ofsaid arms as said rotor rotates to permit said arms to move inwardlyfrom said outward position and a second segment sequentially engageablewith the free ends of said arms as said rotor continues to rotate toreturn each arm to said outward position; a plurality of firstexpandable fluid chambers defined between said housing and said rotoradjacent the free ends of said arms; a plurality of second expandablefluid chambers defined by said arm recesses and the associated arms andsealed from said first chambers by said arm horn members; means toconnect said second fluid chambers to a source of externally pressurizedworking fluid; valve means operable to sequentially direct charges ofsaid working fluid under pressure into said second fluid chambers whensaid first segment of said rotor surface is positioned adjacent the freeend of the associated arm so that said pressurized fluid will operatewithin said second chambers and forcefully urge the associated arminwardly against said rotor and thereby impArt a torque to said rotorand shaft; transfer channel means connecting each of said secondchambers to the first chambers associated with the adjacent followingarm to transfer said charges from said second chambers into saidconnected chambers caused by the movement of the associated arms, tothereby compound the operation of said charges in said first chambersand operate said engine as a compound engine; exhaust means in fluidcommunication with each first fluid chamber and arranged so that outwardmovement of said arms and continued rotation of said rotor forces thefluid from said first chambers through said exhaust means; and meanssealing said side portions of said rotor and arms with respect to saidhousing end walls.
 4. A rotary engine in accordance with claim 1 whereinthe change in volume of the connected first and second fluid chambersoccurs at substantially the same rate so that the fluid charge istransferred from said second to said first chamber without performingsubstantial work on the fluid.
 5. A rotary externally pressurized fluidengine comprising: a housing defining a generally cylindrical rotorspace having parallel end walls; a rotor mounted on a shaft within saidrotor space, said rotor having a substantial transverse surface and sideportions spaced adjacent said end walls; a plurality of elongate armspositioned within generally conforming arm recesses provided around theinner periphery of said housing and spaced uniformly with respect tosaid rotor, each of said arms having side portions spaced adjacent saidend walls and further having one end pivoted to said housing and theother end free to swing between an outward position engaged within theassociated arm recess and an inward position engaged with said rotorsurface; a tapered horn member provided on each of said arms adjacentsaid free arm ends and projecting outwardly into the associated armrecess, each of said horn members having outwardly converging sideedges, with one edge being positioned to slide in sealing engagementwith said housing as said arms move between said inward and outwardpositions; said rotor surface including a first segment sequentiallyengageable with the free ends of said arms as said rotor rotates topermit said arms to move inwardly from said outward position and asecond segment sequentially engageable with the free ends of said armsas said rotor continues to rotate each arm to said outward position; aplurality of first expandable fluid chambers defined between saidhousing and said rotor adjacent the free ends of said arms; a pluralityof second expandable fluid chambers defined by said arm recesses and theassociated arms and sealed from said first chambers by said arm hornmembers; means to connect said second fluid chambers to a source ofexternally pressurized working fluid; valve means operable tosequentially direct charges of said working fluid under pressure intosaid second fluid chambers when said first segment of said rotor surfaceis positioned adjacent the free end of the associated arm so that saidpressurized fluid will operate within said second chambers andforcefully urge the associated arm inwardly against said rotor andthereby impart a torque to said rotor and shaft; transfer channel meansconnecting each of said second chambers to the first chambers associatedwith the adjacent following arm to transfer said charges from saidsecond chambers into said connected chambers caused by the movement ofthe associated arms, to thereby compound the operation of said chargesin said first chambers and operate said engine as a compound engine;means sealing said side portions of said rotor and arms with respect tosaid housing end walls; and exhaust means comprising exhaust portsprovided in at least one of said end walls and a mating valving portionprovided on an adjacent arm, each of said ports being arranged to beclosed by said valving portion when saId adjacent arm is in said outwardposition and to open into fluid communication with one of said firstfluid chambers when said adjacent arm is moved to said inward position.6. A rotary engine in accordance with claim 5 wherein each of saidexhaust ports is arranged to open into fluid communication with thefirst expandable fluid chamber defined by said preceding arm and whereinthe mating valving portion opens each of said ports after the free endof said adjacent arm has engaged said first portion of said rotor andsaid adjacent arm has swung inwardly through a selected arc, so that theexhaust of fluid from said first fluid chamber of said preceding armstarts after torque has been transmitted to said rotor by said adjacentarm.
 7. In a power system having a source of externally pressurizedworking fluid and outlet means for directing pressurized fluid from saidsource, the improvement comprising a rotary engine driven by saidexternally pressurized working fluid, said engine comprising: a housingdefining a generally cylindrical rotor sapce having parallel end walls;a rotor mounted on a shaft within said rotor space, said rotor having asubstantial transverse surface and side portions spaced adjacent saidend walls; a plurality of elongate arms positioned within conforming armrecesses provided around the inner periphery of said housing and spaceduniformly with respect to said rotor, each of said arms having sideportions spaced adjacent said end walls and further having one endpivoted to said housing and the other end free to swing between anoutward position engaged within the associated arm recess and an inwardposition engaged with said rotor surface; a horn member provided on eachof said arms intermediate said arm ends and projecting outwardly intothe associated arm recess, each of said horn members being positioned toslide in the associated recess in sealing engagement with said housingas said arms move between said inward and outward positions; said rotorsurface including a first segment sequentially engageable with the freeends of said arms as said rotor rotates to permit said arms to moveinwardly from said outward position and a second segment sequentiallyengageable with the free ends of said arms as said rotor continues torotate to return each arm to said outward position; a plurality of firstexpandable fluid chambers defined by said housing and the free ends ofsaid arms; a plurality of second expandable fluid chambers defined bysaid arm recesses and the associated arms and sealed from said firstchambers by said arm horn members; means connecting said second chambersin fluid communication with said system outlet means for directing saidpressurized working fluid into said second chambers; valve meansoperable to sequentially admit charges of said pressureized workingfluid from said system outlet means into said second chambers when saidfirst segment of said rotor surface is positioned adjacent the free endof the associated arm so that said fluid charges operate within saidsecond chambers and forcefully urge the associated arm inwardly againstsaid rotor and thereby impart a torque force to said rotor and shaft;transfer channel means connecting each of said second chambers to thefirst chambers associated with the adjacent following arm to transfersaid charges from said second chambers into said connected firstchambers in response to the change in volume of said connected chamberscaused by the movement of associated arms, to thereby compound theoperation of said charges in said first chambers and operate said engineas a compound engine; exhaust means in fluid communication with eachfirst fluid chamber and arranged so that outward movement of said armsand continued rotation of said rotor forces the fluid from said firstchambers through said exhaust means; and means sealing said sideportions of said rotor and said arms with respect to said housing endwalls.
 8. The power system in accordance with claim 7 wherein saidpressurized working fluid comprises compressed gas.
 9. The power systemin accordance with claim 7 wherein the change in volume of the connectedfirst and second chambers occurs at substantially the same rate so thatthe fluid charge is transferred through said channels without performingsubstantial work on the fluid.
 10. The power system in accordance withclaim 7 wherein said source of working fluid comprises a vapor generatorand wherein said pressurized working fluid comprises vapor.
 11. Thepower system in accordance with claim 10 wherein said pressurizedworking fluid comprises superheated vapor.
 12. In a power system havinga source of externally pressurized working fluid and outlet means fordirecting pressurized fluid from said source, the improvement comprisinga rotary engine driven by said externally pressurized working fluid,said engine comprising: a housing defining a generally cylindrical rotorspace having parallel end walls; a rotor mounted on a shaft within saidrotor space, said rotor having a substantial transverse surface and sideportions spaced adjacent said end walls; a plurality of elongate armspositioned within conforming arm recesses provided around the innerperiphery of said housing and spaced uniformly with respect to saidrotor, each of said arms having side portions spaced adjacent said endwalls and further having one end pivoted to said housing and the otherend free to swing between an outward position engaged within theassociated arm recess and an inward position engaged with said rotorsurface; a horn member provided on each of said arms intermediate saidarm ends and projecting outwardly into the associated arm recess, eachof said horn members being positioned to slide in the associated recessin sealing engagement with said housing as said arms move between saidinward and outward positions; said rotor surface including a firstsegment sequentially engageable with the free ends of said arms as saidrotor rotates to permit said arms to move inwardly from said outwardposition and a second segment sequentially engageable with the free endsof said arms as said rotor continues to rotate to return each arm tosaid outward position; a plurality of first expandable fluid chambersdefined by said housing and the free ends of said arms; a plurality ofsecond expandable fluid chambers defined by said arm recesses and theassociated arms and sealed from said first chambers by said arm hornmembers; transfer channels connecting each second fluid chamber in fluidcommunication with a first fluid chamber associated with another arm;conduit means connecting each first fluid chamber in fluid communicationwith the second chamber associated with the same arm; transfer valvemeans in fluid communication with said first chambers and selectivelyoperable in one position to sequentially direct charges of saidpressurized fluid into said chambers so that said charges operatesimultaneously in the first and second chambers connected by saidconduit means and impart a force to the adjacent arm when said firstsegment of said rotor is positioned adjacent the free end of saidadjacent arm, to operate said engine as a simple engine; said transfervalve means being further operable in a second position to sequentiallydirect charges of said fluid into said second chambers for intialoperation when said first segment of said rotor is positioned adjacentthe free end of the associated arm so that the following movement ofsaid arms changes the volumes of the first and second chambers connectedby said transfer channels and transfers said charges from said secondchambers to said first chambers through said transfer channels, topermit said charges to expand further in said first chambers and therebyoperate said engine as a compound engine; exhaust means in fluidcommunication with each first fluid chamber and arrangeD so that outwardmovement of said arms forces the fluid from said second chambers intothe connected first chamber and forces the fluid from said firstchambers through said exhaust means; and means sealing said sideportions of said rotor and arms with respect to said housing end walls;whereby said transfer valve means permits said engine to be switchablebetween simple and compound modes of operation.
 13. A power system inaccordance with claim 12 wherein the volumes of the first and secondchambers connected by said transfer channels change at substantially thesame rate as the fluid charge is transferred through said transferchannels from the first chambers to the connected second chambers sothat the fluid transfer occurs without performing substantial work onthe fluid.
 14. A method of transmitting torque to the output shaft of anengine having a rotor mounted on said shaft and disposed within a sealedhousing having a plurality of swinging arms uniformly positioned aroundthe rotor within the housing and adapted to impart a torque force to therotor when driven inwardly against the rotor, with said arms includingarcuate projections extending outwardly in sliding engagement with saidhousing, said projections and housing defining first and secondexpandable fluid chambers adjacent each of said arms, said method ofcomprising the steps of: providing the engine with a source ofexternally pressurized working fluid; admitting a first charge of saidpressurized working fluid from said source into each of said first fluidchambers so that the charges operate within said first chambers againstthe associated arms and drive said arms inwardly against said rotor;timing the admission of said charges into said first fluid chambers sothat the operation of said charges within said first chambers drivessaid arms sequentially inward against said rotor; transferring saidcharges from each of said first fluid chambers into the second fluidchamber provided adjacent another arm; further directing said fluidcharges in said second chambers inwardly against the rotor and theadjacent arms to drive the adjacent arms inwardly against the rotor;admitting a second charge of pressurized working fluid from said sourceinto each of said first fluid chambers; timing the admission of saidsecond charges with said valve means so that said second charges operateinwardly against the associated arm simultaneously with the operation ofsaid transferred charges within said second chambers; and sequentiallyexhausting each of said charges from said second fluid chambers aftersaid further operation through exhaust means timed so that theexhaustion of fluid from said second chambers begins after theoverlapping operation of said second charges in said first fluidchambers; whereby a continuous torque force is transmitted to said rotorby the overlapping operation of charges of pressurized working fluidagainst said rotor and arms and the operation of each charge of fluid iscompounded to provide said engine with a compound mode of operation. 15.The method in accordance with claim 14 wherein said fluid charges aretransferred from said first chambers to said second chambers withoutperforming substantial work on the transferred fluid.
 16. The method inaccordance with claim 14 wherein said pressurized working fluidcomprises compressed gas.
 17. The method in accordance with claim 14wherein said source of working fluid comprises a vapor generator, andwherein said pressurized working fluid comprises vapor.
 18. The methodin accordance with claim 17 wherein said vapor comprises superheatedvapor.
 19. A method of transmitting torque to the output shaft of anengine having a rotor mounted on said shaft and disposed within a sealedhousing and having a plurality of swinging arms uniformly positionedaround the rotor within the housing and adapted to impart a torque forceto the rotor when driven inwardly Against the rotor, with arms includingarcuate projections extending outwardly in sliding engagement with saidhousing, said projections and housing defining first and secondexpandable fluid chambers adjacent each of said arms, said methodcomprising the steps of: providing the engine with a source ofexternally pressurized working fluid; admitting a first charge of saidpressurized working fluid into each of said first and second chambers sothat said first charge operates within adjacent first and secondchambers simultaneously against the same arm to drive the arm inwardlyagainst said rotor; timing the admission of said first charges into saidchambers so that the operation of said first charges drives said armssequentially inward against said rotor and so that the operation of saidfirst charges against the rotor and the adjacent arms overlap in time;sequentially exhausting said first charges from said chambers; admittinga second charge of said pressurized working fluid into each of saidfirst chambers; timing the admission of said second charges into saidfirst chambers so that the operation of said charges against said armsdrives said arms sequentially inward against said rotor; transferringsaid second charges from each of said first chambers into the secondchamber provided adjacent another arm; directing said second charges insaid second chambers inwardly against the adjacent arms to further drivesaid arms sequentially inward against said rotor; and sequentiallyexhausting each of said second charges from said second chambers;whereby said first charges of working fluid operate said engine as asimple engine and said second charges of working fluid operate saidengine as a compound engine.